Stage 5.1 — Warehouse ERP: batches + FIFO + reservations + multi-warehouse

Schema:
- warehouses (multi-warehouse, code unique per company, is_default)
- part_batches (lot per receipt, qty_in/qty_remaining, buy_price, FIFO-indexed)
- warehouse_events (immutable ledger: opening/receipt/issue/transfer/adjustment/write_off)
- part_reservations (per-WO allocations from specific batches, active/consumed/released)
- companies.default_warehouse_id + parts.qty_reserved

Backfill: 1 default warehouse + 1 opening batch per existing part per company.

WarehouseService:
- receive / issue (FIFO) / reserve / release / consume / transfer / adjust
- DB::transaction + lockForUpdate on batch rows
- InsufficientStockException with requested + available context
- Auto-syncs parts.qty as aggregate cache (source of truth = sum(qty_remaining))

WO integration:
- WorkOrderPart created/updated → reserve from FIFO batches
- WorkOrderPart deleted → release
- WorkOrder status=done → consume reservations into issue events
- WorkOrder status=cancelled → release reservations

Filament:
- WarehouseResource (CRUD)
- BatchesRelationManager on PartResource (FIFO list with qty_remaining + cost)
- "Recepție" action on parts list → calls WarehouseService::receive
- qty_reserved column added on parts list

Tests (8 new, all pass):
- receipt creates batch + event
- FIFO order verified across 3 batches with different received_at
- InsufficientStockException on over-issue
- Reservations block other reservations but don't deplete on-hand
- WO done consumes; WO cancelled releases
- Batches tenant-isolated
- Transfer between warehouses with weighted-avg cost

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/Services/Warehouse/InsufficientStockException.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace App\Services\Warehouse;
+
+class InsufficientStockException extends \RuntimeException
+{
+    public function __construct(
+        public readonly int $partId,
+        public readonly float $requested,
+        public readonly float $available,
+    ) {
+        parent::__construct(sprintf(
+            'Stoc insuficient pentru piesa #%d: cerut %.3f, disponibil %.3f',
+            $partId, $requested, $available
+        ));
+    }
+}